When you buy/sell via an exchange, try to use limit orders (try not to use market orders). Limit orders generally have the lowest fees, market orders generally have higher fees. On GDAX, limit orders are free as long as they don’t fill immediately (meanwhile, market orders result in a .3% fee, that is better than the 1.4% Coinbase charges, but not as good as 0%… especially if you are day trading).